It is evident that, to build a column made of, for example, reinforced concrete, a mould or formwork is needed to provide the column with its configuration and dimensions, said formwork requiring two different and complementary features: on the one hand it has to ensure a perfect superficial finish of the columns and on the other hand, especially when the formwork is disposable, its cost has to be sufficiently low to make it profitable for the builder.
In the field of disposable formworks for the manufacture of cylindrical columns, formworks are known based on a tubular body, made of paperboard, with its internal side covered by a waterproof liner thus avoiding the deterioration of the paperboard due to the humidity generated from the concrete, said liner being obtained from an aluminium complex. The tubular body has, additionally, another external liner, generally plasticised, to protect likewise the paperboard and to mark the product externally.
For the manufacture of columns with polygonal section, for example columns with a square section, polystyrene plates duly configured to be adapted externally to the cylindrical wall of the tube and to form, as a whole, the desired polygonal section of the column, are established and attached conveniently inside said tubular body.
The above-mentioned solutions, although they are functionally valid, are structurally complex and economically expensive. They present, furthermore, some limitations regarding the possibilities to design certain types of columns due to the fact that the filling plates have to be introduced and to be attached inside the tubular pre-existing body.